A Palladium-Catalyzed Method for the Synthesis of 2-(α-Styryl)-2,3-dihydroquinazolin-4-ones and 3-(α-Styryl)-3,4-dihydro-1,2,4-benzothiadiazine-1,1-dioxide: Access to 2-(α-Styryl)quinazolin-4(3H)-ones and 3-(α-Styryl)-1,2,4-benzothiadiazine-1,1-dioxides

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An efficient synthesis of 2-(α-styryl)-2,3-dihydroquinazolin-4-ones and 3-(α-styryl)-3,4-dihydro-1,2,4-benzothiadiazine-1,1-dioxides has been achieved in 39-94% yield through palladium-catalyzed cyclocondensation of aryl/vinyl iodides with allenamides 13-15 and 22, respectively. Base treatment of the N-tosylated products provides an easy access to 2-(α-styryl)quinazolin-4(3H)-ones and 3-(α-styryl)-1,2,4-benzothiadiazine-1,1-dioxides, hitherto unknown heterocycles. The method has been tested with phenyl substituted allenamides, applied for bis-heteroannulation, and used in the preparation of analogues of the natural product Luotonin F.